The present invention relates generally to the field of feedback controllers.
Feedback controllers are used to control variable devices such as valves, pumps, and dampers in control systems or processes (e.g., a heating and cooling system). The object of such controllers is to control the device in a way that maintains a controlled variable (e.g., temperature, humidity, flow rate, pressure, etc.) at a desired setpoint. Many feedback controllers respond to feedback based on one or more control parameters. A common control parameter used in feedback algorithms is proportional gain (i.e., the proportional term, the gain, etc.)—a value that is used by a feedback algorithm to determine the magnitude of the adjustment to the controlled signal given the error signal. For example, when provided the same error signal, a feedback algorithm with a high gain generally results in a large adjustment to the controlled signal while a small gain generally results in a small adjustment to the controlled signal. In addition to the proportional gain, other control parameters such as integral term or derivative term are often used by feedback algorithms (e.g., in proportional plus integral (PI) control algorithms, in proportional-integral-derivative (PID) control algorithms, etc.).
In dynamic systems (e.g., wherein conditions outside of the control loop are affecting the controlling variable or where an aspect of the control loop is variably imperfect), the optimal control parameters for the feedback algorithm are also dynamic. Accordingly, some feedback controllers or feedback algorithms are periodically tuned (e.g., manually, automatically) based on observed historical behavior of the system. Other feedback controllers or feedback algorithms include adaptive tuning algorithms that automatically adjust the control parameters during normal operation of the feedback algorithm. Such adaptive tuning algorithms can provide for improved performance relative to tuning algorithms that run only periodically.